The present invention relates to a preform for forming a one-piece disposable (i.e. single service) plastic container (e.g. a bottle) of the champagne base variety having an annular peripheral chime surrounding an inward sloping base portion for containing carbonated beverages, the container resisting inversion of the base caused by internal pressure comprising the use of an integral reinforcing ring incorporated into the base and running horizontally in the hoop direction, the reinforcing ring being placed in a location within the base that has a moment arm trying to invert the base and providing sufficient strength to withstand that moment arm and keep the push up of the inward sloping portion intact by expanding an elongate preform containing the plastic material for the neck, body and base of the bottle into a mold. The preform is formed with annular thickened portions of the preform shaped and positioned along the length thereof such that during blowing of the preform the material of the preform will be deposited so that the inward sloping base portion and the chime have a distribution of material which will resist deformation which will otherwise occur as a result of the moment arm created around the chime by internal pressure to prevent unrolling and radial stretching of the chime sufficient to allow inversion of the inward sloping base portion.
One aspect of plastic bottle production by blow molding techniques which is known in the art is the use of varying wall thicknesses at critical points of stress, such as in the neck and capping threads A good example of such a prior art approach and the apparatus employed therewith can be seen with reference to U.S. Letters Pat. No. 3,137,748 to Makowski. FIG. 1 hereof depicts the apparatus of Makowski in simplified form. As shown in FIG. 1, a double two-part mold 24 is used to create a preform 26 of the plastic to be used for the bottle. The mold 24 has a neck-producing portion 28 and a bottle-producing portion 30. A hollow core pin 32 is inserted into the assembled mold 24 and the preform 26 made by injecting the plastic through a sprew hole at 34. The bottle-producing portion 30 of the mold 24 must be a two-part or split mold since the core pin 32 is cylindrical and the preform 26 contains areas of various thickness to provide additional material for various areas of the finished bottle.
The preform 26 with the core pin 32 therein and the neck-producing portion 28 of the mold 24 in place is removed from the bottle-producing portion 30 following the injection molding procedure and mounted to a blow mold having a bottle-defining cavity therein. As known by those skilled in the art, various considerations relative to the temperature of the preform prior to the actual blow molding step must be accounted for. The core pin 32 of Makowski is hollow and contains an integral valve (not shown) at the bottom end thereof. With the preform 26 positioned within a cavity, the valve is opened and pressurized air is injected causing the preform 26 to stretch outward from the bottom up to fill the cavity and thereby create the final bottle.
The Makowski patent is not directed to producing a pressure-resistant bottle. The variations in thickness of the preform 26 are to provide different amounts of material available for stretching to form various parts of the bottles shown therein which are of complex shape, such as those used for dishwashing liquids and the like. There is no need for the accurate placement of integral reinforcement-producing areas. Moreover, the preform design with respect to the cylindrical core pin 32 makes the use of a more costly and complex two-part or split injection mold for the production of the preform a necessity.
Wherefore, 1L is an object of the present invention to provide a cost effective preform for forming a one piece plastic bottle for containing carbonated beverages which is of the champagne type but which resists inversion from internal forces using a minimum of material without the necessity of including complex rib structures therein.
It is a further object of the present invention to provide a preform which can be produced in a simple one-part injection mold.
It is yet another object of the present invention to provide a preform in which the reinforcing sections can accommodate encountered inaccuracies in positioning during the blow molding process.
It is yet another object of the present invention to provide a preform shape with increased heat dissipating surface area in areas of increased thickness.
Further objects and advantages of the present invention will become apparent from the description contained hereinafter in combination with the accompanying illustrative drawing figures.